This application claims the priority of Korean Patent Application No. 2003-21406, filed on Apr. 4, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a gap measurement apparatus and a method thereof used in an exposure process performed when a semiconductor device and a display are manufactured, and more particularly, to an apparatus for measuring a gap between a mask and a substrate and a method thereof.
2. Description of the Related Art
In general, a semiconductor device and a display are used as essential elements of supporting information electronic technologies. In an exposure process used to manufacture such semiconductor device and display, a gap between a mask and a substrate (semiconductor substrate or glass substrate) serves as an important factor of determining an exposure quality. Thus, it is essential in the exposure process to measure the gap between the mask and the substrate exactly and adjust the gap. An operation of measuring a gap between two substrates and adjusting the gap is widely used in a variety of fields, except for the exposure process.
FIG. 1 illustrates a conventional gap measurement apparatus using a charge coupled device (CCD).
Specifically, in the conventional gap measurement apparatus, when a laser oscillator 51 emits laser beams, the laser beam passes a first lens 53 and reaches a mask M and a substrate S at a predetermined angle using a first reflector 55. A part of the laser beam is reflected from a lower surface of the mask M, and other part thereof is reflected from an upper surface of the substrate S and passes a second lens 63 using a second reflector 61 via different paths. A two-dimensional CCD 65 recognizes light-receiving positions of two laser beams transmitted via the different paths and transmits coordinate values thereof to a signal processing unit 67. The signal processing unit 67 calculates a gap between the mask M and the substrate S using a difference between the coordinate values and transmits a gap value to a controller 69. An image obtained by the two-dimensional CCD 65 is transmitted to an image processing unit 70 and displayed visually on a monitor.
However, the conventional gap measurement apparatus of FIG. 1 performs gap measurement by recognizing positions of reflected laser beams using the two-dimensional CCD 65. However, the price of the conventional gap measurement apparatus of FIG. 1 is high, and the gap measurement apparatus cannot simply measure a gap between a mask and a substrate at a desired position of a large area.